Disaster(ous) Planning: On Floods, Food and Soil....

[J A Ginsburg]

I grabbed this map from a New Scientist article on the global food crisis, "What Price More Food" (Debora Mackenzie, June 11, 2008), which, unfortunately, is locked behind a subscription wall. If you can get hold of a copy, it's one of the better analyses of how we got ourselves in such a fix -- and it was written long before the Floods of '08 (in the U.S, China, Myanmar, Kenya, the Phillipines...).

Although dated 1992, the map provides a good snapshot of where the bulk of the world's food comes from, and why massive crop losses in Iowa, Wisconsin, Illinois, Indiana and Missouri is such devastating news. (see the FAO's "Undernourished Map").

Unlike the 100 mph+ fury of a hurricane or the lightning fast (often lightning-spawned) advance of a wildfire ("Calif. firefighters fighting hundreds of blazes"), flood waters can take days and even weeks to meander down the Mississippi and its tributaries. Levees are breeched, towns drowned, and farmland turned into lakes under sunny skies with barely a cloud in sight.

(photo: Todd Heisler/ The New York Times /"Call for Change Ignored, Levees Remain Patchy ")

Ironically, levees themselves often make the situation worse by forcing enormous volumes of water into a straight-jacketed channels.

Adding Up Costs
The extent of the crop losses have yet to be tallied, but whether measured in dollars (billions) or acres (millions) or percentages (at least 20% of Iowa's corn crop), it's serious. Even if the land dries out enough to plant, it's probably too late for this season. Soy has a shorter growing season than corn, but soy plants would wither in cornfields sprayed with herbicides. One man's cash crop is another man's inconvenient weed. In any case, the general rule of green thumb is to leave fields potentially contaminated with who knows what fallow for at least 120 days (pathogens can travel into and onto plants via water).

But it is going to take a lot more time -- years, decades, maybe longer -- to rebuild what's been lost soil-wise ("Heavy rains, flooding bring severe soil erosion"). While a 3 to 5 ton annual loss per acre of topsoil is considered "normal" in Iowa (still kind of horrifying), 7 to 8 tons per acre have been lost in a single day during the recent storms. It takes anywhere from 500 to 1,000 years to form an inch of soil. You do the math.

Actually, others have done the math and it is grim: According to a 2006 study, the U.S. is losing soil at 10 times the replenishment rate. In China and India, it's 30 to 40 times. Globally, soil erosion is a $400 billion problem (likely more now), and over the last 40 years, a third of the world's arable land has become unproductive.

Worlds Below
Lately, I have been on a real kick with books about food and dirt ("Tales from the Underground: A Natural History of Subterranean Life," "Dirt: The Erosion of Civilizations," "Life in Soil: A Guide for Naturalists and Gardeners," "The Earth Moved: On the Remarkable Achievements of Earthworms," "Animal, Vegetable, Miracle: A Year in Food Life")

It turns out that there is more biota beneath the surface than above it. In fact, one could make a pretty good argument that the surface exists to service what's beneath. About 90% of all plants, and just about every kind of tree, depend on fungi that infiltrate roots to access key minerals and sources of water that even the even the most diaphanous of root hairs are too big to reach. Trees will sacrifice as much as 1/3 of the energy profits of photosynthesis in trade. For every ton of prairie you see, there are 3 tons worth of roots you don't. Legumes, including soy, are famous for their symbiotic partnerships with bacteria that are capable of "fixing" nitrogen from the air, changing it into a form the plants can use. Then there are all the little creatures that crawl and slither through the earth or slide on thin films between soil particles, plowing the dirt and creating rich, fertile humus (a word with shares a root, btw, with "human" and "humble" -- the Middle Eastern dish made from chickpeas is "hummus").

So enamored was Charles Darwin of earthworms, he filled his study with terrariums so he could watch them at work. His last book was devoted to them: "The Formation of Vegetable Mould Through the Action of Worms." Through years of experiments, often working with his sons, he came to the stunning conclusion that earthworm "casts" could account for as much as 10 tons of soil per acre being brought to the surface. And they're not the only ones busy down there.

Which got me wondering how the flood might be affecting the invisible worlds below. I wrote to Jim Nardi, a biologist at the Illinois History Survey and the author of "Life in the Soil" (University of Chicago Press):

"Not many people even think about what effects the flooding has on soil health. Not only do the flood waters leach nutrients from the soil but they also disrupt the soil structure and whatever soil aggregates are present. Most life in the soil is devastated. Some creatures such as tardigrades and rotifers can enter a state of suspended animation (cryptobiosis) until the flooding subsides, but most soil arthropods (insects, millipedes, mites, springtails, sowbugs, spiders, etc.) and other invertebrates such as earthworms, potworms, nematodes, snails are doomed. Aerobic microbes suffer a similar fate. And even many of the larger soil aerators and mixers such as moles, ground squirrels and gophers are unable to escape. However, there are always some species of earthworms, nematodes, potworms and microbes that can survive these conditions; these are species that normally inhabit soil that is seasonally submerged by winter and spring flood waters. Some soil insects whose larvae live in soil but whose adults fly (crane flies, midges, many beetles, scorpionflies) may quickly repopulate the soil if the adult insects had emerged from the soil before flooding began. After the floodwaters subside, different organisms begin the process of recolonizing the soil that had been submerged and purged of so much life. The rate of this process will vary depending on the size and mobility of the creatures.

I doubt that any serious study has been conducted of the effects of flooding on soil life and re-colonization of the soil after the flooding - a study similar to that undertaken at Mount St. Helens and Krakatoa after the volcanic eruptions that eliminated life from their slopes."

Ph.D. thesis anyone?

Doing Less to Save More
At the very least, it gives even more reason to invest in erosion control and environmentally-friendly farming practices such as no-till planting: "Save the Sowbugs!" Although no-till requires some investment and patience to get started, it also reduces a farmer's carbon footprint. In fact, no till farming is traded as a carbon offset on the Chicago Climate Exchange. Now there's some good news...